Further analysis revealed Krt18 and Krt20, which are selectively expressed in S-cells of controls (Fig. 1b,c), co-localized with Fabp4 and Pparg in K14-BC-positive cells in the basal layer (Fig. 1g–k), suggesting that the VP16;Pparg transgene is inducing K14-Basal cells to differentiate into S-cells in situ. This evidence concerns the gene KRT18 and breast cancer.